Retail Outlets LLC Contracts with Smooth Paving Inc

Retail Outlets LLC contracts with Smooth Paving Inc. to grade and pave a parking lot. The contract provides that it cannot be assigned without Retail's consent. Later, Smooth assigns the contract to Tough Road Company without obtaining Retail's consent. Retail could most successfully argue that the contract cannot be assigned because

A) the assignment is prohibited by statute.
B) the contract is personal.
C) the assignment will materially change a risk.
D) the contract prohibits assignment.